Role of sodium on H+ excretion in the integument of the leopard frog Rana pipiens

1. The northern leopard frog, Rana pipiens, pipiens, in contrast to the southern leopard frog, Rana pipiens, berlandieri, did not demonstrate any significant H+ excretion across its integument even during a challenge of chronic metabolic acidosis. Likewise, no increase in the number of H+ secreting mitochondria-rich cells were observed in the northern frogs. 2. Under normal acid-base conditions in the southern frogs, H+ excretion was found to be dependent on mucosal sodium concentrations, whereas during chronic metabolic acidosis, H+ excretion was independent of mucosal sodium concentrations, but was amiloride sensitive. 3. High salinity adapted southern frogs, under normal and acidotic conditions, had enhanced H+ excretion rates as compared to the control non-salt adapted frogs. 4. Blood analyses demonstrated that significant acid-base changes were the result of systemic acidosis and not due to salt adaptations. Blood Na+ and K+ concentrations were also efficiently maintained during salt adaptations or chronic metabolic acidosis. 5. The results suggest that H+ excretion in epithelia can be influenced by the sodium transport state of the cell and the systemic acid-base profile. Models are proposed explaining these relationships.     

Plant phosphoglucose isomerase genes lack introns and are expressed in Escherichia coli

Nuclear genes that appear to encode both cytosolic and plastid isozymes of phosphoglucose isomerase (PGI), an essential glycolytic enzyme, have been isolated from three diploid species of the annual wild flower genus Clarkia (Onagraceae). The genes do not contain introns and are expressed to varying degrees in Escherichia coli when cloned in either Charon 35 phage or pUC plasmid vectors. The PGI proteins synthesized in E. coli form dimers, are catalytically active, and their electrophoretic mobilities are similar to those of appropriate Clarkia PGIs. The nucleotide sequence of a gene encoding a plastid isozyme of C. unguiculata is described.     

Acid proteinase activity in fish--I. Comparative study of extraction of cathepsins B and D from Mujil auratus

Acid catheptic activity was measured in crude extracts of muscle, liver, heart, spleen and gonads from the fishes Mujil auratus, Sparus aurata and Lightonatus mormyrus. The spleen was the organ which showed the highest activity. A comparative study of the seven most commonly used extraction methods was made. Some were modified to account for the characteristics of the fish organs and the activity extracted from them. The Siebert method resulted as the best extraction method only if 1 mM EDTA was present in the medium. The activity from Mujil auratus muscle was strongly inhibited by iodoacetate, N-ethylmaleimide, p-hydroxy mercuribenzoate, and diazo-acetyl-DL-norleucine methyl ester. The results indicated the presence of a carboxyl-proteinase and a thiol-proteinase. According to inhibition studies, the levels of proteinase and amidase activities shown by different organs of Mujil auratus were re-examined. The spleen extract showed the maximum activity for both cathepsins, but muscle extract accounted for more than 95% of total catheptic activity.     

Spectrophotometric assay of phenolpthalein in biological fluids.

An assay for phenolphthalein in biological fluids has been developed utilizing methods previously applied to the assay of bromosulphalein and to the deconjugation of steroidal compounds in urine. Intestinal perfusate, serum, and urine samples containing phenolphthalein are deproteinized with acidified acetone, the samples dried, and the phenolphthalein redissolved in ethanol. Color is developed with 0.5 m glycine buffer, pH 12, and the samples read at 550 nm after blanking the spectrophotometer with one of the replicates to which acidic glycine buffer is added. To measure conjugated phenolphthalein in urine, the sample is incubated overnight with β-glucuronidase/arylsulphatase prior to phenolphthalein determination as noted above. This method gives an accurate assay of phenolphthalein to 10^?5m concentrations with coefficients of variation between 2 and 8% and with no resulting interference from hemoglobin or bilirubin.     

Induction of erythroid differentiation by cytoplast fusion in mouse erythroleukemia (Friend) cells

An intracellular activity, which is induced by dimethyl sulfoxide (DMSO) or hexamethylenebisacetamide (HMBA) and leads to erythroid differentiation in mouse Friend cells, was characterized by cell fusion between genetically marked intact cells and cytoplasts. For this, a procedure for rapid selection of cybrids was devised by sensitizing non-fused cells with oligomycin. We were able to demonstrate that cytoplasts derived from DMSO- (or HMBA)-treated cells trigger erythroid differentiation upon fusion with UV-irradiated cells. The activity in the cytoplasts remained only transiently and its induction was inhibited by biologically active phorbol esters or cycloheximide. The activity, however, was not induced in cytoplasts by directly treating them with DMSO (or HMBA). These results indicate that (1) the intracellular erythroid-inducing activity is located in cytoplasts, (2) it acts in trans and induces erythroid differentiation as a dominant factor and (3) its production requires de novo nuclear protein synthesis. The mechanisms of the induction of the intracellular activity and of how it triggers erythroid differentiation are discussed.     

The regeneration and maturation of mast cells following peritoneal lavage in the rat

Adult rats subjected to repeated peritoneal saline lavage show a rapid depletion of mast cells in the peritoneal fluid, but the mast cells in mesentery and omentum are not significantly reduced. The residual mast cells are predominantly young elements, histochemically belonging to stages 1 and 2 of maturation. Regeneration of mast cells is rapid with return to the normal density and distribution accomplished within 3 -- 4 weeks after cessation of lavage. The origin, nature and factors influencing the regeneration of mast cells is to be further investigated.     

Clinical effectiveness of biologics in clinical practice

TNF inhibitors are currently considered both effective and cost-effective in patients with active rheumatoid arthritis (RA), particularly in patients who have not responded fully to methotrexate. There is substantial doubt about the cost-effectiveness of TNF inhibitors as initial treatment for active RA. New data from the National Data Bank for Rheumatic Diseases now question the current consensus in methotrexate failures. The data suggest that in routine clinical practice TNF inhibitors provide only modest incremental benefits over best conventional therapy. If confirmed, these observational studies suggest that the economic argument underpinning the widespread use of TNF inhibitors in established RA is unsustainable.